Marcel de Rooy authored Jul 19, 2017 and joubu committed Dec 07, 2017

In order to allow multiple Koha to MARC mappings (for one kohafield), we
need to adjust a few key routines in C4/Biblio.pm. This results in a few
changes in dependent modules too.

Note: Multiple mappings also include 'alternating' mappings. Such as the
case of MARC21 260 and 264: only one of both fields will be used. Sub
TransformMarcToKoha will handle that just fine; the opposite transformation
is harder, since we do no longer know which field was the source. In that
case TransformKohaToMarc will fill both fields. We only use that operation
in Koha for items (in Acquisition and Cataloging).

Sub GetMarcSubfieldStructure
This sub used a selectall_hashref, which is fine as long as we have only
one mapping for each kohafield. But as DBI states it: If a row has the same
key as an earlier row then it replaces the earlier row. In other words,
we lose the first mapping if we have two.
This patch uses selectall_arrayref with Slice and rearranges the output so
that the returned hash returns an arrayref of hashrefs for each kohafield.
In order to improve consistency, we add an order clause to the SQL
statement used too.

Sub GetMarcFromKohaField
This sub just returned one tag and subfield, but in case of multiple
mappings we should return them all now.
Note: Many calls still expect just one result and will work just fine:
    my ($tag, $sub) = GetMarcFromKohaField(...)
A possible second mapping would be silently ignored. Often the sub is
called for biblionumber or itemnumber. I would not recommend the use of
multiple mappings for such fields btw.
In case the sub is called in scalar context, it will return only the first
tag (instead of the number of tags and subfields).

Sub GetMarcSubfieldStructureFromKohaField
This sub previously returned the hash for one kohafield.
In scalar context it will behave like before: it returns the first hashref
in the arrayref that comes from GetMarcSubfieldStructure.
In list context, it returns an array of all hashrefs (incl. multiple
mappings).
The sub is not used in C4::Ris. Removed the use statement.

Sub TransformKohaToMarc
This sub got a second parameter: frameworkcode.
Historically, Koha more or less assumes kohafields to be defined across all
frameworks (see Koha to MARC mappings). Therefore it falls back to Default
when it is not passed.
When going thru all mappings in building a MARC record, it also supports
multiple mappings. Note that Koha uses this routine in Acquisition and in
Cataloging for items. Normally the MARC record is leading however and the
Koha fields are derivatives for optimization and reporting.

The added third parameter allows for passing a new option no_split => 1.
We use this option in C4::Items::Item2Marc; if two item fields are mapped to
one kohafield but would have different values (which would be very unusual),
these values are glued together. When transforming to MARC again, we do not
want to duplicate the item subfields, but we keep the glued value in both
subfields. This operation only affects items, since we are not doing this
reverse operation for biblio and biblioitem fields.

Sub _get_inverted_marc_field_map
This sub is a helper routine of TransformMarcToKoha, the opposite
transformation. When saving a MARC record, all kohafields are extracted
including multiple mappings.
Suppose that you had both 260c and 264c in your record (which you won't),
than both values get saved initially into copyrightdate like A | B. The
additional code for copyrightdate will extract the first year from this
string.
A small fix in TransformMarcToKoha makes that it only saves a value in a
kohafield if it is defined and not empty. (Same for concatenation.)

Sub TransformMarcToKohaOneField
This sub now just calls TransformMarcToKoha and extracts the requested
field. Note that since we are caching the structure, this does not result
in additional database access and is therefore performance-wise
insignificant. We simplify code and maintenance.
Instead of modifying the passed hashref, it simply returns a value. A call
in C4::Breeding is adjusted accordingly. The routine getKohaField in
Koha::MetadataRecord is redirected to TransformMarcToKohaOneField.
NOTE: The fourth patch restructures/optimizes TransformMarcToKoha[OneField].

Sub get_koha_field_from_marc
This sub can be removed. A call is replaced by TransformMarcToKohaOneField
in C4::XISBN.

Note: The commented lines for sub ModZebrafiles are removed (directly under
TransformMarcToKohaOneField).

Test plan:
For unit tests and interface tests, please see follow-ups.
Run qa tools in order to verify that the modules still compile well.
Read the code changes and verify that they make sense.

Signed-off-by: Josef Moravec <josef.moravec@gmail.com>

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>

Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>